1. Field of the Invention
The present invention relates to a light-emitting device, and more particularly, to a structural arrangement of a wavelength conversion member in a light-emitting device in which a chip of a laser diode is used as a light-emitting element.
2. Description of the Related Art
A light-emitting device in which a chip of a laser diode (LD) or a light-emitting diode (LED) is used as a light-emitting element is small in size, is of low power consumption, and has a long service life. Hence, such a light-emitting device is used in a wide range of the fields, e.g., backlight of a liquid crystal display, onboard use, and the like. Light emitted by such light-emitting elements is monochromatic light of limited colors such as red, green, and blue. Such light-emitting elements are sometimes used in combination with a fluorescent substance for converting the monochromatic light into light of a different wavelength. For example, a light-emitting device is known in which light from a light-emitting element directly output to the outside, light emitted by the light-emitting element, and wavelength-converted light emitted by a fluorescent substance are color-mixed with one another, thereby emitting white-colored light.
Incidentally, in Jpn. Pat. Appln. KOKAI Publication No. 11-87784, disclosed is an LED device having a shell-like shape whose surface is equipped or covered with a translucent covering member or a translucent covering layer containing a fluorescent substance for wavelength conversion; a material of the translucent covering member or the covering layer; and a fluorescent substance contained in the material, and the like.
Further, in Jpn. Pat. Appln. KOKAI Publication No. 2003-258308, it is disclosed that light emitted by an LED is converted into light of another color by a color conversion member made of glass into which an inorganic fluorescent substance is added and dispersed, and that in a use in which glass is required to have a high mechanical strength, it is desirable that a thickness of the glass be 0.2 mm or larger, from the viewpoint of mechanical strength.
Further, in Jpn. Pat. Appln. KOKAI Publication No. 2005-20010, a white light-emitting device is disclosed in which a fluorescent composition is placed such that the composition receives light from an LD, and the fluorescent composition emits light having a wavelength longer than the light from the LD.
On the other hand, in Jpn. Pat. Appln. KOKAI Publication No. 2003-295319, a light source device is disclosed in which laser light is absorbed by a fluorescent substance and which emits incoherent light.